Screening for pre-eclampsia using sFlt-1/PlGF ratio cut-off of 38 at 30-37 weeks' gestation

Objective: To evaluate the soluble fms-like tyrosine kinase 1 (sFLT-1) to placental growth factor (PLGF) ratio cut-off of 38 for prediction of preeclampsia (PE) in routine assessment in singleton pregnancies at 30-37 weeks’ gestation.

Methods: This was a prospective observational study in women attending for a third-trimester ultrasound scan at 30-37 weeks as part of routine pregnancy care. Serum sFlt-1 and PlGF were measured and their ratio calculated. We estimated the detection rate (DR), false positive rate (FPR), positive predictive value (PPV) and negative predictive value (NPV) of sFLT-1/PLGF >38 for prediction of delivery with PE at <1, <4 and >4 weeks after assessment.

Results: The study population of 12,305 singleton pregnancies was examined at a median of 32.4 (range 30.0-36.9) weeks and included 14 (0.11%), 77 (0.63%) and 227 (1.84%) that subsequently delivered with PE at < 1, < 4 or > 4 weeks’ after assessment, respectively. The DR, FPR, PPV and NPV of sFLT-1/PLGF >38 in the prediction of delivery with PE at <1 week were 78.6%, 4.5%, 1.9% and 99.97%, respectively. The respective values for delivery with PE at <4 weeks were 76.6%, 4.1%, 10.4% and 99.85% and for delivery with PE at >4 weeks were 20.7%, 4.3%, 8.3% and 98.47%.

Conclusion: In routine screening of singleton pregnancies, the performance of sFLT 1/PLGF >38 is modest for prediction of delivery with PE at <1 and <4 weeks and poor for prediction of PE at 4 weeks. The sFLT-1/PLGF >38 predicted 79% of cases with PE at <1 week at FPR of 4.5%; consequently, a policy of hospitalizing patients with this ratio would potentially lead to unnecessary hospitalization in 4.5% of pregnancies and a ratio of <38 would falsely reassure one fifth of the women that will deliver with PE at <1 week from assessment.

Fetal Medicine Foundation. Grant Number: 1037116